This invention relates to the catalytic alkylation of a isoparaffin with one or more olefins. In one of its aspects this invention relates to apparatus for carrying out alkylation. In another of its aspects, this invention relates to apparatus and process employing dual reactors with a single settling vessel. In a further aspect of the invention, it relates to the recycle of reactor product effluent from the settler as a portion of reactor feed stock.
The catalytic alkylation of an isoparaffin with one or more olefins to produce a branched chain paraffin is a commercially important process for producing high-octane gasoline. Conventional catalytic alkylation processes usually involve the reaction of an isoparaffin, such as isobutane, with olefin, such as propylene, or, optionally, both propylene and a butene, in the presence of a liquid alkylation catalyst, such as hydrogen fluoride, followed by the separation of the unreacted feed stock and product hydrocarbons from the catalyst in a settling zone and the purification of the product alkylate by fractionation. It has now been found that a general process improvement over standard production using a single reactor can be accomplished by using dual reactors discharging product effluent into a common settler and by recycling a portion of the reacted product effluent from the settler as feed stock to the reaction. The benefits of the dual reactor process include improved alkylate quality and the reduction of the feed volume to the alkylate fractionator. The reduction of feed volume to the alkylate fractionator is important because the fractionator is a principal consumer of utilities in an alkylation plant. The invention is, therefore, useful to effect economies in the fractionator of a new plant, to increase the capacity of an existing plant by installing the novel two-reactor system and/or to increase alkylate product quality.
It is therefore an object of this invention to provide a method and apparatus for improving the alkylate quality in the alkylation of isoparaffin and olefin in the presence of a catalyst as compared to the quality of alkylate produced in a similar operation using standard single reactor operation. It is another object of this invention to provide a method and apparatus for reducing the load on the alkylate fractionator in a catalytic alkylation process as compared to a standard single-reactor catalyzed alkylation process. It is also an object of this invention to provide method and apparatus for reducing the overall utility requirement in an alkylation plant. It is also an object of this invention to provide method and apparatus for improving the capacity of an existing alkylation plant.
Other aspects, objects, and the various advantages of this invention will become apparent upon reading this specification and the appended claims in conjunction with the drawings.